Retroperitoneal Hybrid Nerve Sheath Tumor Mimicking Malignant Imaging Manifestations: A Rare Case Report

Abstract Background: Hybrid peripheral nerve sheath tumors (hPNSTs) is an exceedingly rare benign peripheral nerve sheath tumor, featuring elements from at least two nerve sheath tumor cells. We herein report a rare case of retroperitoneal HNST manifesting malignant imaging features.

Case presentation

We reported a 40-year-old female presented with unexplained abdominal pain, with no significant personal or familial medical history. Imaging workup revealed a large solid-cystic retroperitoneal mass with internal hemorrhage, calcification and cystic degeneration. The lesion showed restricted diffusion and progressive delayed enhancement on MRI, with blurred borders adjacent to major retroperitoneal vessels and the right ureter, highly suggestive of an invasive malignant tumor. The patient underwent complete surgical resection. Postoperative histopathology and immunohistochemistry confirmed a benign hybrid schwannoma/neurofibroma, with no lymph node metastasis identified. The patient recovered uneventfully and remained recurrence-free during follow-up.